CHEMICAL CONSTITUTION AND PHARMACOLOGICAL ACTION 413 



the molecule. In many cases the color thus passes through red into 

 violet, in other cases it passes into brown. Besides this the chemistry 

 of the rosanilin dyes furnishes many examples of change in tint through 

 the introduction of substituting groups; thus, rosanilin red; tri- 

 methylrosanilin red violet; hexamethylrosanilin blue violet; tri- 

 phenylrosanilin blue. 



I may add that in several cases these views have been applied 

 also to bodies possessing physiological action. In cocaine, for ex- 

 ample, the ester-like benzoyl radical, (CO-C 6 H 5 ), undoubtedly repre- 

 sents the ansesthesiophore group; the tertiary amin contained in the 

 basic portion representing an analogue of the auxochrome group, 

 and hence called auxotox. This is borne out by the fact determined 

 by me that cocaine loses its anaesthetizing properties when through 

 methylation the tertiary amin is converted into a quaternary ammo- 

 nium base. Analogous to this is the fact that through complete 

 methylation tertiary groups lose the property to act as auxochromes, 

 for the ammonium radicals thus formed merely give rise to an in- 

 creased solubility. Thus through the introduction of a methyl group, 

 hexamethyl violet, which possesses three dimethylamido radicals, 

 passes over into the soluble methyl^ green, which possesses two di- 

 methylamido groups and one ammonium group. Hence methyl green 

 is a triphenyl-methan dye which contains two dimethylamido groups 

 as auxochromes. In this it is like malachite green, which it therefore 

 matches entirely in tint. 



The third portion of the cocaine molecule, the carboxylmethyl 

 group, COOCH 3 , on the other hand, is probably of but little im- 

 portance, as can be seen from the strong anaesthetic action of benzoyl- 

 pseudotropein, which does not possess this group. 



III. 



Having thus briefly sketched some of the more important points 

 concerning the relation between chemical constitution and action, 

 I pass on the pharmacological side of the subject, in which, to be 

 sure, the conditions are far more complex. It will be well to com- 

 mence with a very simple example. We know a large number of 

 poisons which through appropriate substitution are practically de- 

 prived of their deleterious action. As was shown by Aronson and 

 myself, this is true, especially of the radicals of sulphuric and carbonic 

 acids. Independently of us, Nencki came to the same conclusion. 



